The Boeing 737-300 is the oldest aircraft in Southwest’s current fleet. The main differences from the -700 are a smaller tail, different landing lights, and different color flaps/fairings.
They were retrofitted a few years ago…maybe to make them more efficient? I have traveled in this type of plane and with the same airline twice…disgracefully they’re going to retire it soon.
The -200 winglet is developed by Quiet Wing Corp, which adds it as part of a flap modification kit certified in 2005 by the FAA, which mostly improves performance in general on the aircraft.
Aviation Partners Boeing (with information from their company website here) retrofits all 737 classic/NextGen winglets, which mostly involves strengthening the wing structure, adding flutter ballast, and replacing the wings’ ribs and cockpit systems before adding the winglet itself. The FAA got the STC for the Classics all the way back in 2003. It costs about USD 750.000 to install and offers some benefits, including improved climb and cruise performance and decreased emissions from the aircraft. More info can be found here and here.
I don’t think it’s necessary. Externally, it looks almost exactly like a 737-700, and besides, as mentioned above they’re retiring them soon. As much as I love the plane, I don’t think it’s necessary.
The plane is vastly different from the 700 as the wings and tail are completely different. I think the 733/734/735 would be a great addition to the 737 family we already have in game.